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Setting the GDB safe-path cross platform

I've been developing an embedded Rust app (yay!) on Windows (blegh) recently. The Rust team have put incredible effort into making Rust itself work great in Windows environments, but the tooling around it can be difficult to get working correctly. My current problem was making GDB load a .gdbinit file from the current projecting when doing xargo run. Here's how I fixed it in .cargo/config:

# .cargo/config
runner = [ "arm-none-eabi-gdb.exe", "-iex", "set auto-load safe-path ." ]
rustflags = [
  "-C", "link-arg=-Tlink.x",
  "-C", "linker=arm-none-eabi-ld",
  "-Z", "linker-flavor=ld",
  "-Z", "thinlto=no",

The key is being able to pass arguments to the runner = line. Nailing arguments onto the end of a string didn't work, which was frustrating. As far as I can tell, the array syntax for the runner = [ ... ] line isn't documented, but it allows you to append command line arguments that aren't mishandled by GDB.

The main kicker for cross platform "compatibility" is setting safe-path to .. Setting this to anything else will result in weird problems with a \backslashy\windows\path\ending\with\a\unix/path. GDB moans that this isn't a real path, which is true, but sucks for actually getting the thing working. This of course requires you to have a .gdbinit file in your project root.

Easy peasy.